1. Field of the Invention
The invention relates to a parallel adjustment device for a print head carriage guide relative to a print medium support in printers, and in particular in matrix printers, where the print head carriage guide comprises a carriage guide axle disposed at the rear of the printer frame and which carriage guide axle can be adjusted parallel to the print medium support and a front carriage guide axle disposed opposite to the print medium support and disposed at a minimum distance and where the rear and the front carriage guide axle in each case is supported in the side plates of the printer frame and where the print medium support is disposed at a height level different from that of the front carriage guide axle.
2. Brief Description of the Background of the Invention Including Prior Art
Such parallel adjustment devices for a print head carriage guide serve the purpose to maintain the distance of the print head along the full length of the print path. The print path is slightly shorter as compared to the length of the print medium support of the same size. Such distance maintenance is of importance in particular for flat print medium supports of importance. On the other hand, the print head motion has to remain always on the same height level of the print head during the print path, that is during the full print path, in order to avoid an inclined line and in addition in order to remain always on the horizontal line of a bundle of vertical tangents. In case of an arched print medium support, that is, in case of a so called print platen. It is of importance in this context that the distance of the print head from the print medium support in an inclined position, for example, in case of needle print heads, has to remain within the stroke of the needle, that is about 0.2 to 0.4 mm.
According to technology employed in the factory, where this invention was made, hitherto employed parallel setting devices formed of axle supports, which axle supports can be shifted in parallel within the plane of the side plate. The setting of such axle supports is difficult as there is lacking any measure for the adjustment path and as the axle support have to be adjusted based on feeling and guess work. Therefore such a parallel positioning is difficult to achieve during assembly, it is time consuming and remains relatively imperfect.